In a semiconductor device as a power device which is in heavy use for power control, a temperature rises with increase in operating current. There are some cases where the semiconductor device is extremely heavily used, and in such cases, the rising temperature might exceed a threshold limit to cause multifunction of the semiconductor device or lead to damage thereto.
Therefore, for example in an invention disclosed in Patent Document 1, a semiconductor device is designed such that a diode temperature sensor is formed inside the semiconductor chip to monitor a temperature of a semiconductor chip, and in the case of detecting an extreme temperature rise, the operation of the semiconductor device is controlled.
Patent Document 1: Japanese Patent Laid-Open No. 2000-31290
As a conventionally used temperature sensor other than this sensor, an IC temperature sensor can be cited. These temperature sensors allow a minute electric current to flow and then monitor an output voltage so as to detect a temperature. Both sensors have the characteristic of being capable of measuring a large range of temperatures, but an output voltage per 1° C. changes to a small degree and an amount of such a change is several mV.
Therefore, detection of the amount of change requires provision of a highly accurate detection circuit capable of detecting an output voltage difference of several mV. Further, there is a problem in that, since an environment where the semiconductor device is used is a high-noise environment, the minute electric current is drowned out by the noise and the temperature cannot be sufficiently monitored.
Moreover, although the diode temperature sensor can be directly set on the semiconductor chip, this makes variations large and causes a problem in terms of accuracy in temperature measurement.
The IC temperature sensor is accurate in temperature measurement, but cannot be directly set on the semiconductor chip, and hence there is no choice but to measure the temperature via a heat conduction material. For this reason, heat resistance of the IC temperature sensor in the semiconductor chip becomes a problem, thereby making it difficult also for this sensor to perform accurate temperature measurement.
Since the respective temperature sensors have the problems as thus described, it is difficult for a semiconductor device using either of such temperature sensors to accurately monitor a temperature of a semiconductor chip in a noise environment.